Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface showing the first image in a sequence, showing our new design;

FIG. 2 is a front view showing the second image thereof; and,

FIG. 3 is a front view showing the third image thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 to 3. The process or period in which one image transitions to another forms no part of the claimed design.

The outer perimeters illustrated by broken lines in the drawings depict a display screen or portion thereof and forms no part of the claimed design. The remaining broken lines depict portions of graphical user interface that form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 